Positioning mechanisms find wide application in industry, research, and military environments. For low-tolerance application in friendly environments, simple two-stage devices having mechanical bearings are frequently adequate. However, for high-precision applications, such as the increasingly fine positioning required in lithography systems used in applications such as semiconductor manufacture, mechanical systems frequently have neither the accuracy, speed, nor reliability required. Further, since such applications are frequently carried out in "clean-room" environments where space is at a premium, and sometimes in low-pressure environments where air-bearings cannot be utilized, magnetic actuators and bearings having as small a footprint as possible are becoming increasingly important options. Magnetic actuators are also advantageous in that they are frictionless, thereby allowing more accurate operation, not generating particles which may result from mechanical bearings and operating at higher speed. Further, magnetic bearings are capable of each providing multiple degrees of freedom, thereby permitting an actuator to provide multiple degrees of freedom with a lesser number of bearings/actuators than would be required with comparable mechanical structures. An example of such a magnetic positioner is shown in "Design and Analysis Framework For Linear Permanent-Magnet Machines," David L. Trumper, Won-Jong, Kim and Mark E. Williams, I.E.E.E. Transactions on Industry Applications, 1232 Vol. 32 No. 2, March-April, 1996, pp. 371-79. Other such magnetic positioner systems are shown in U.S. Pat. No. 5,699,621 issued Dec. 23, 1997 entitled POSITIONER WITH LONG TRAVEL IN TWO DIMENSIONS, and U.S. Pat. No. 5,631,618 issued May 20, 1997 entitled MAGNETIC ARRAYS, both of which are assigned to the Assignee of the current application.
While such systems function well in most applications, there are applications, such as those in a clean-room environment or where the positioner is being used in a satellite or space station, where a need exists to keep size to a minimum and to make the system as power-efficient as possible. A need therefore, exists for an improved magnetic positioner which is more compact and more power-efficient than such prior systems, while still providing long travel for a single moving platform or stage in two dimensions and short travel or position control for the stage in the remaining four dimensions.